Spin flow necking is a process of necking-in an open end of a metal container to ultimately provide a flange which allows a can end to be seamed thereto after filling. Necking also makes conveying of the cans easier since, with only slight flange overlap, the cans contact body-to-body instead of flange-to-flange which would otherwise cause tilting and conveying jams.
While numerous necking processes have been developed since the 1970's, a particularly promising spin flow process and apparatus having the potential of allowing can ends to be necked-in to increasingly smaller diameters is disclosed in U.S. Pat. No. 4,781,047, issued Nov. 1, 1988 to Bressan, which is assigned to Ball Corporation and is exclusively licensed to the assignee of the present invention, Reynolds Metals Company. The disclosure of this patent is hereby incorporated by reference herein in its entirety. It concerns a process where an externally located free spinning form roll 11 (FIG. 1) is moved inward and axially against the outside wall C' of the open end C' of a rotating trimmed can C to form a conical neck at the open end thereof. With further reference to FIG. 1, a spring-loaded holder or slide roll 19 supports the interior wall of the can C and moves axially under the forming force of the form roll 11. This is a single operation where the can C rotates and the form roll 11 rotates so that a smooth conical necked end is produced. In practice, the can is then flanged. The term "spin flow necking" is used in this application to refer to such processes and apparatus, the essential difference between spin flow necking and other types of spin necking being the axial movement of both the external roll 11 and the internal support 19.
More specifically, the exemplary spin flow tooling assembly 10 depicted in FIG. 1 (corresponding to FIG. 1 of the Bressan et al '047 patent, supra) includes a necking spindle shaft 16a rotatable about its axis of rotation A by means of a spindle gear 16 mounted to the shaft between front and rear bearings (not shown). The slide roll 19 is mounted to the front end of the necking spindle shaft 16a through a slide mechanism 28, keyed to the shaft, which permits co-rotation of the roll 19 while allowing it to be slid by the necking forces described more fully below in the axially rearward direction B' away from the eccentric freewheeling roll 24 located adjacent the front face of the slide roll. The axially fixed eccentric idler roll 24, having an axis of rotation B which is parallel to and rotatable about spindle axis A, is mounted via bearings 16b and 23 to an eccentrically formed front end of an eccentric roll support shaft 18. This shaft 18 extends through the necking spindle shaft 16a. The spindle shaft 16a is rotated by the spindle gear 16 without rotating the eccentric roll support shaft 18.
The outer form roll 11 is mounted radially outwardly adjacent the slide and eccentric rolls 19,24.
The container slide roll 19 is shaped with a conical leading edge 19a designed to first engage the open end C" of the container C to support same for rotation about spindle axis A under the driving action of the necking spindle gear 16 which may be driven by the same drive mechanism driving each base pad assembly 29 engaging the container bottom wall. Slide roll 19 is also free to slide axially but is resiliently biased into the container open end C" via springs 20 which may be of the compression type.
In operation, the container open end C" engages and is rotated by the slide roll 19. The eccentric roll 24 is then rotated into engagement with a part of the inside surface of the container side wall C' located inwardly adjacent the open end C". With reference to FIGS. 2A-2E, the external form roll 11 then begins to move radially inward into contact with the container side wall C' spanning the gap respectively formed between the conical faces 19a,24e of the slide and eccentric rolls 19,24. More specifically, the side wall C' of the spinning container body C is initially a straight cylindrical section of generally uniform diameter and thickness which may extend from a pre-neck (not shown) previously formed in the container side wall such as by static die necking. As the external form roll 11 engages the container side wall C', it commences to penetrate the gap between the fixed internal eccentric roll 24 and the axially movable slide roll 19, forming a truncated cone (FIG. 2B). The side wall of the cone increases in length as does the height of the cone as the external form roll chamfer 11c continues to squeeze or press the container metal along the complemental slope or truncated cone 24e of the eccentric roll 24 as depicted in FIG. 2C. The cone continues to be generated as the external form roll 11 advances radially inwardly (the slide roll 19 continues to retract axially as a result of direct pushing contact from roll 11 through the metal) until a reduced diameter 124 is achieved as depicted in FIGS. 2C and 2D. As the cone is being formed, the necked-in portion 124 or throat of the container C conforms to the shape of the forming portion of the form roll 11. The rim portions 123 of the neck which extend radially outwardly from the necked-in portion 124 are being formed by the complemental tapers 11b,19a of the form roll 11 and the slide roll 19 to complete the necked-in portion.
The above-described spin flow necking process, while producing a large diameter reduction in the open end of the container C (e.g., 0.350"), has various drawbacks when applied to two-piece aluminum can manufacture. One drawback, for example, is grooving of the neck at the initial point of contact between rolls 11,19 in FIG. 2B which occurs on the inside of the container as a result of the small radii on the form roll pushing past and against the small radii on the slide roll as the form roll moves radially inwardly and axially rearwardly during the necking process along the chamfer 24e of the eccentric roll. Due to the force of spring 20 urging the slide roll 19 toward the eccentric roll 24, the metal caught between these colliding radii (which are forcefully pressed together under spring bias), is grooved on both the inner and outer surfaces of the neck. On the inside surface, this grooving results in metal exposure (i.e., wearing away of the protective coating) which often allows the beverage to "eat through" the container side wall C'. It has also been discovered that such grooving often results in actual cutting of the metal as the form roll 11 is radially inwardly advanced from the position depicted in FIG. 2B to that of FIG. 2C.
As the form roll 11 moves into its radially inwardmost position depicted in FIG. 2E, the spring pressure acting against the slide roll 19 in the direction of the form roll disadvantageously results in pinching of the end of the flange-like portion 123 and undesirable thinning of the metal. In some cases, particularly when necking a can to smaller diameters (e.g., 204 or 202), the edge is sometimes thinned down to a knife edge.
To prevent both grooving of the container side wall and excessive thinning of the flange type edge during the aforementioned spin flow necking process, a cam ring is secured to the slide roll to present a cam follower surface which is contacted by the form roll during radial inward advancing movement of the latter at the on-set of the necking-in process. The cam follower surface and the conical surface of the form roll facing the cam follower surface are further arranged to produce the following motions:
In FIG. 3A, the form roll axis has moved radially inwardly closer to the container axis and has started to form the neck. The conical surface 24e on the eccentric roll 24 has forced the form roll 11 toward the open end C" of the container C. The form roll 11 has just touched the cam follower surface 104. The small radius 106 on the form roll 11 is very close to the small radius 108 on the slide roll 19' but does not pinch the metal between these two points. This is because the cam ring follower surface 104 is positioned so these radii 106,108 may approach each other but stay separated by a distance slightly greater than the initial side wall thickness. This is presently understood to be a key feature in the elimination of metal exposure and neck cracks caused by excessive contact pressure between the two small radii 106,108 in the uncontrolled collision of the form roll 11 with the metal wrapped around the small radii 108 on the slide roll 19 in the prior spin flow necking process described hereinabove. In other words, since the form roll 11 contacts the cam follower surface 104 as the two radii 106,108 approach, such contact results in retraction or rearward axial sliding movement of the slide roll 19' which permits the two radii to move past each other.
In FIG. 3B, the form roll 11 has penetrated further between the eccentric roll 24 and the slide roll 19'. The small radius 106 on the form roll 11 is just passing the small radius 108 on the slide roll 19'. The rolls 11,19' do not pinch the metal but have moved closer. As mentioned above, the form roll 11 is forcing the slide roll 19' back by contact between the form roll and the cam ring 102 instead of contact at this point between the form roll and the slide roll as occurred in the aforesaid prior spin flow necking process.
In FIG. 3C, the form roll 11 has continued its penetration and the small radius 106 is past the small radius 108 on the slide roll 19' (point A). At this point, the conical surfaces 19a,11b on the slide roll and the form roll, respectively, are opposite and parallel each other. The slide roll 19' and cam ring 102 have been pushed to the left in FIG. 3C. The combination of the metal thickening as a result of being squeezed between the form roll 11 and the eccentric roll 24 as the metal wraps around the forming surface 11a of the form roll, and the shape of the left or trailing conical surface 11b on the form roll, has reduced the relative clearance between the form roll and the slide roll so that the form roll is now actually putting slight pressure on the metal.
In FIG. 3D, the form roll 11 has now penetrated further into the gap between the eccentric and slide rolls 24,19'. The form roll 11 is clearly clamping the metal between it and the slide roll 19' and, as a result, a gap 130 has opened up between the form roll surface 11b and the cam ring follower surface 104. The form roll 11 is now pushing the slide roll 19' directly in the axially rearward direction through its contact with the metal, and not through the cam ring 102. Since the small radii 106,108 between the form roll 11 and slide roll 19' have already "slipped" past each other without undesirable grooving of the metal therebetween, the direct interaction of the form roll in thinning and shaping the metal against the bias of the conical surface 19a on the slide roll is important to ensure proper necking and distribution of metal.
In FIG. 3E, the form roll 11 has now penetrated to its radially inwardmost position to complete the formation of the spin flow neck. During the entire forming process, between 20 to 24 revolutions of the container C are required, depending on the diameter, thickness and the amount of diameter reduction in the container end. The rolling contact between the form roll 11 and the slide roll 19' has thinned the edge of the flange slightly. Therefore, in accordance with a further feature of this invention, the form roll 11 now once again contacts the cam ring 102 to prevent further thinning of the flange area of the container C, i.e., gap 130 has closed.
The foregoing cam ring improvement to the spin flow necking process is disclosed in U.S. patent application Ser. No. 07/929,933, filed Aug. 14, 1992, by Harry W. Lee, Jr. et al, now U.S. Pat. No. 5,245,848, issued Sep. 21, 1993, patent which is assigned to Reynolds Metals Company, the assignee of the present application. The disclosure of this patent is hereby incorporated by reference herein in its entirety.
The cam ring advantageously eliminates the grooving and cut necks, as well as excessive thinning of the flange, that were prevalent before its introduction. However, the interaction of the outer form roll with the eccentric and slide rolls to achieve the final necked-in state depicted in either FIG. 2E (no cam ring) or FIG. 3E (with cam ring) has been discovered, through extensive experimentation, to directly affect the plug diameter (i.e., the inner diameter of the necked-in portion such as measured at 124 in FIG. 2E) and the length of flange 123, with or without the cam ring, and at any given base pad setting (i.e., the fixed distance during necking between the base pad 29 supporting the can bottom and the axially immovable eccentric roll), resulting in unacceptable variations therein. In a can plant environment, particularly when employing numerous necking-in tooling assemblies in a multi-station machine of the type disclosed in U.S. patent application Ser. No. 07/929,932, filed Aug. 14, 1992, by Harry W. Lee, Jr. et al, entitled "Spin Flow Necking Apparatus and Method of Handling Cans Therein", now U.S. Pat. No. 5,282,375, issued Feb. 1, 1994, also assigned to Reynolds Metals Company, the present assignee, control over the plug diameter and flange width achieved with the tooling assembly at each station is critical to achieving homogeneity in product and successful continuous operation. The disclosure of the '375 patent is hereby incorporated by reference herein in its entirety.
To obtain acceptable plug diameter variations, U.S. patent application Ser. No. 07/953,421, filed Sep. 29, 1992, by Harry W. Lee, Jr. et al, now U.S. Pat. No. 5,349,836, issued Sep. 27, 1994, also assigned to Reynolds Metals Company, discloses spin flow necking tooling assembly 1000 in FIG. 4 wherein a plurality of identical stop spacers 1025 are bolted to the front end of the spindle mounting assembly with bolts 1044 located radially outwardly from the path of movement of the slide roll 19. The spacers 1025 extend radially inward from mounting screws 1044 to define a series of equi-spaced stop surfaces 1050 which are co-planar to each other and intersect the plane of axial movement of the rear facing shoulder 1052 of the slide roll 19.
An exemplary embodiment of such a machine is depicted in FIG. 1A of the U.S. Pat. No. 5,282,375, (hereinafter "the '375 patent"), incorporated herein by reference. Except as noted hereinbelow, the tooling assembly 1000 of FIG. 4A functions in a manner identical to the tooling assembly of FIG. 5 (incorporated herein by reference) disclosed in the '375 patent. Briefly, the eccentric roll 24 is rotated from its eccentric solid line position depicted in FIG. 4A in supporting contact with the can open end into a radially inward clearance position (not shown) via rotation of the pinion 108 through a plurality of tooling activation assemblies 200 mounted to the rear face of the tooling disc turret. FIG. 5 herein corresponds to FIG. 7 (the written disclosure of which is incorporated by reference herein) of '375 patent. Therein, it can be seen that rotation of pinion 108 as well as radial movement of form roll 11 (supported by shaft 1010) is controlled through a series of radially extending linkage arrangements 210 respectively interconnecting each tooling activation assembly 200 to a cam follower 204 in rolling contact with a cam surface 206 of a cam ring which is stationarily mounted to a support frame supporting the tooling disc turret. Further relevant details of FIG. 5 will be discussed hereinbelow.
With the stop spacers 1025 of FIG. 4A, as the form roll 11 is moved towards its radially innermost position of FIG. 3E under the action of cam follower 204 of FIG. 5 which rotates shaft 1010 through activation plate 275, the rear surface 1052 of the slide roll 19' contacts the stop surface 1050 of spacers 1025 which prevents further axial retraction of the slide roll assembly. This was expected to prevent or "freeze" final radial movement of form roll 11 which would otherwise occur solely as a result of contact between cam follower 204 with cam surface 206. In this manner, the final radial positioning of outer form roll 11 was intended to be controlled by the contact between the slide roll 19' with the spacers 1025 which axially "locks" the slide roll to override final radially inward camming movement of the outer form roll 11. Therefore, since the final radially inwardmost location of forming surface 11a of form roll 11 is now controlled by the stop spacer arrangement 1025 described supra, the resulting plug diameter formed by this surface 11a tended to be more uniform. Stated differently, as the form roll 11 is forced into the gap between the eccentric roll 24 and the slide roll 19, the slide roll is forced away from the eccentric roll as discussed in connection with FIGS. 3A-3D. When the slide roll assembly 19 hits the stop spacers 1025, movement of the slide roll is halted. This in turn stops further inward radial travel of form roll 11. The eccentric roll 24 is axially rigid so when the slide roll 19 hits the stop surface 1050, the gap cannot get any wider. Therefore, the form roll 11 must stop.
Although it is theoretically possible to stop the movement of the slide roll 19 in the necking tooling of the FIG. 1 embodiment (no cam ring) by placement of a spacer attached to collar 21 to contact the rear shoulder of slide roll 19', this is very difficult in practice. This is because when the form roll 11 forces the slide roll 19' against the stop surface 1025 in FIG. 4A, the force of the form roll that is moving the slide roll toward the stop acts through the cam ring and not through the can flange itself which would otherwise occur without the cam ring. The force required to actually form the can is approximately 80-100 pounds and the override spring 279 (FIG. 5) located on the side of the necking turret is pre-loaded to about 200-250 pounds. Since the cam follower movement transmitted through this spring 279 from cam follower 204 (FIG. 5) to the form roll 11 is a part of the mechanism which controls radial movement of the form roll, when the slide roll stops the form roll, it overrides this spring and the force of the form roll therefore builds from 80-100 pounds up to 200-250 pounds. This extra force must be supported by the cam ring on one side of the form roll and the eccentric roll and the can neck on the other side of the form roll. Therefore, if the cam ring is not used, the force required to stop the form roll must come from the slide roll face through the can flange to the form roll as in FIG. 1. This force on such a narrow can flange would be enough to roll the flange to a thin knife edge which unacceptably causes split flanges and uneven flange width.
Although the spring pre-load force cannot act upon the can material between slide roll 19 and form roll 11 as a result of the cam ring 102, a force vector corresponding to the full pre-load spring force acts directly on the eccentric roll 24 and a necked-in portion of the can extending between the rolls 11,24 as depicted in FIG. 3E. Consequently, this full force spring pre-load tends to cause either grooving or wearing away of the protective coating on the interior surface of the can contacting the eccentric roll 24. This can disadvantageously allow the beverage to "eat through" the container side wall. In addition, since the eccentric roll 24 is cantilevered relative to slide roll 19 through a small sub-shaft, it is theorized that there is a tendency for the eccentric roll to be deflected radially inwardly. It is believed that this uncontrolled deflection creates considerable and undesirable variation in plug diameter of the can open end and flange width to a lesser degree, particularly within the lower range of dimensional variation as a result of the radially inward deflecting movement of the eccentric roll under the spring pre-load force.
It is accordingly an object of the present invention to prevent unacceptable variations in can plug diameter and flange width during the spin flow necking process.
Another object is to control the inner action of the outer form roll with the inner eccentric roll to ensure such uniformity in plug diameters and acceptable plug diameter variation.
Still another object is to control the inner action of the outer form roll with both the inner slide roll and inner eccentric roll to ensure the aforesaid uniformity and acceptable variation.
Yet another object is to prevent excessive force from being transmitted from the outer form roll to the inner eccentric roll through the can material so that the final radially inward advancing movement is directly controlled by controlling movement of the outer form roll.
Yet another object is to provide a control mechanism that may be installed in each tooling assembly so as to pre-set the final radially inward movement of the outer form roll either in the plant tool room or on the production floor after installation of the assemblies in a multi-station machine, to achieve the aforesaid uniformity in plug diameter.
Yet another object is to provide a plug diameter control mechanism which is simple in design, easy to install, and capable of rugged continuous operation without wear.